Field of the Invention
The present invention relates to moving a movable element relative to a fixed body, and more precisely it relates to an electromechanical actuator suitable for use by way of example in aviation, and in particular for moving a flight control surface relative to the structure of an aircraft. By way of example, such a flight control surface may be an aileron, an elevon, a flap, a rudder control surface, an elevator, a spoiler, . . . .
Aircraft generally comprise a fixed structure, such as a wing or a tail, having flight control surfaces hinged thereto that are mounted on the fixed structure so as to pivot. Actuators connect the movable surfaces mechanically to the fixed structure and are themselves connected so as to be controlled by a control unit on which the pilot of the aircraft acts.
Description of Related Art
Actuators are known that comprise an electric motor and a motion transmission element driven by a rotor of the electric motor. Generally, in such actuators, the electric motor has a stator secured to a body that is fastened to the fixed structure, and a transmission element drives an inlet element of a transmission system such as a screw-and-nut assembly and/or stepdown gearing, with an outlet element fastened to the flight control surface so that a movement of the outlet element causes the flight control surface to pivot between a deployed position and a retracted position or a neutral position.
In the event of a failure of the motor or of its control means, and depending on the type of flight control surface, it may be preferable to leave the flight control surface free to move towards one of its positions while preventing the flight control surface from moving towards the second of its positions, e.g. under the effect of aerodynamic forces. For this purpose, the transmission assembly generally includes an overrunning clutch or “freewheel” that can become clutched in the event of motor failure in order to oppose pivoting of the transmission element in the direction corresponding to the flight control surface moving towards its second position.
When the freewheel is clutched, the flight control surface tending to move towards its deployed position exerts a torque on the transmission element, which torque is transmitted to the body. Under certain circumstances, the torque can be large and risks damaging the entire transmission system all the way to the structure of the aircraft.